The present invention relates generally to thrust bearings.
In order to increase the load carrying capacity of a thrust bearing when reaching maximum permissible load of the individual segments, it is necessary in the case of a constant shaft diameter to increase the bearing surfaces of the segments. The load capacity can be increased by increasing the size of the shaft thrust collar whereby the segments can be geometrically widened.
These measures are nevertheless not advantageous in the case of relatively large bearing diameters and fast-running shafts. On the inside part of the segments, i.e., the part lying closest to the shaft, laminar lubricating flows prevail whereas, on the outside circumference, turbulent flow conditions prevail. Owing to this dissimilarity in lubricating wall conditions, the load carrying capacity of the bearing segments is continuously, unfavorably affected over the entire bearing surface such that the load capacity varies in magnitude to the inside and outside circumference of the bearing segments.
Accordingly, it is an object of the present invention to provide a thrust bearing in which a uniform load capacity on the bearing segments is achieved and in which differing flow conditions of the lubricant are avoided.
These and other objects are realized in a thrust bearing according to the present invention wherein the thrust bearing includes a shaft thrust collar arranged in steps. The stepped construction features an inside bearing surface and an outside bearing surface axially offset with respect to the inner bearing surface. Each bearing surface is provided with a spring-supported bearing unit.
Owing to the stepwise construction of the shaft collar and by reason of a distribution of the entire bearing surface over the bearing segments, the individual segments can be constructed smaller than usual without decreasing the load carrying capacity of the bearing. Therefore, more advantageous lubricating and cooling conditions are provided in the bearing since each series of segments can be provided individually with lubricant.
According to a further, more particular arrangement of the thrust bearing according to the invention, each bearing unit consists of one bearing segment, one knuckle washer and a flexible supporting bridge which are all connected to one another by a connecting pin such that the bearing segments are mobile in both the radial and the circumferential direction. Contact surfaces of the knuckle washer are constructed convexly adjacent both the bearing segment as well as the supporting bridge.
The arrangement of a knuckle washer with an elastic supporting bridge in each bearing unit enables an individual adjustment of the flexibility of each supporting bridge. Thereby the axial play between the shaft thrust collar and the individual bearing segments may be individually adjusted. Hence, the inside and outside bearing segment series can be adjusted with respect to each other and allow the bearing to be optimally adapted to operating conditions. The knuckle washer acts simultaneously as a compensation device and a universal coupling between the fleixble supporting bridge and the bearing segment. By this arrangement, each segment of the bearing can be independently adapted to changes on the bearing surfaces.
Further, it is advantageous to provide a separate set of oil delivery and discharge lines disposed in the bearing body for the inside and outside bearing surfaces with a seal provided between the two bearing surfaces. The oil delivery and discharge lines are preferably to be uniformly distributed over the entire bearing circumference.
By the arrangement of separate oil delivery and discharge lines for each bearing surface, it is possible for each segment series to be supplied individually with lubricant. Advantageously, the lubricant pressure in the outside bearing component is set higher than the pressure in the inside bearing component to prevent heated oil from passing over into the outside segment space from the inside segment space by centrifugal force and thereby reduce the load carrying capacity of the outside bearing segments.